Many procedures that are performed in biochemical laboratories involve analyses of multiple samples or materials distributed over a two-dimensional area. Examples of such procedures are screening studies performed on substances that are placed in individual wells of a multi-well plate such as a standard 96-well microtiter plate or larger plates, or on molecular species that are applied as droplets or regularly spaced spots, either microscopic in size or larger, on a solid surface. Further examples are slab-shaped electrophoresis gels in which either two-dimensional electrophoretic separations or one-dimensional separations of multiple samples in parallel have been performed. Still further examples are blotting membranes to which electrophoretically separated species in the form of spots or bands have been transferred from a slab gel. Other examples will readily occur to the skilled biochemist. In all of these examples, detections and analyses of the individual sites in the two-dimensional array are often achieved by light energy associated with each site, and may consist simply of determinations of the presence or absence of particular species or may also include quantitative determinations, either on an absolute basis or as comparisons among different sites. The light energy can be transmissive, absorptive, reflective, or generated by the materials at the sites themselves. Species in electrophoresis gels or blotting membranes, for example, are commonly detected by fluorescence, chemiluminescence, or bioluminescence, either as inherent characteristics of the species at the sites or as a result of treatment of the species once they are separated throughout the two-dimensional array. The treatment may include binding reactions in which energy-emitting labels are attached to the species, or irradiation of the species or the labels with excitation energy that will cause them to emit light energy, most often at different wavelengths.
The two-dimensional array, or the planar matrix supporting the array, can be relatively large, for example exceeding about 5 cm, 10 cm, 20 cm, or even 30 cm, in either length, width, or both. In terms of ranges, the length, width, or both, can for example be from about 3 cm to about 100 cm, from about 10 cm to about 75 cm, from about 5 cm to about 50 cm, or from about 5 cm to about 25 cm. In some cases, a large two-dimensional array is divided into a number of narrow strips for independent analysis. In these cases, one may wish to analyze a single strip, two or more but less than all strips, or all strips of the array. When any of these images is taken by a camera, including digital cameras, the arrays are large enough to require placing the camera a considerable distance from the array. One consequence of placing the camera far from the array is that less light is captured. More light can be captured by placing the camera or image acquisition device closer to the array, but this often requires the use of multiple lenses and other optical components to obtain the full image. Some lenses distort the image and geometric resolution can be of limited quality. Intensity roll-off further distorts the image. A type of camera that is commonly used for imaging in biochemical applications is a charge coupled device (CCD) camera, but even with such a camera and its lenses and other optical components, the sensors must be placed well above the object plane, causing the entire apparatus to consume a large amount of space in the laboratory.